Construction Of Biocatalyst Based On Covalent Organic Frame Materials And The Catalytic Performance

Enzyme is a catalyst with the advantages of specificity and high efficiency,which has a wide application prospect in environmental treatment,oil industry and food processing.However,the structure of enzyme molecules is easily affected by the environment.The free enzyme has disadvantages such as difficulty in separation,difficulty in reusability and low stability in practical application.Enzyme mimic and Immobilized enzyme could overcome these problems due to they possess the advantages of easy preparation,high stability and simple preparation process.So these are effective ways to achieve the goal of green chemistry.In this work,a functional material with catalytic activity and a carrier with core-shell structure were synthesized from the covalent organic framework.The lipase was immobilized with the carrier and applied to the esterification reaction.This study mainly includes the following three aspects:（1）The functional material with catalytic activity was synthesized by coordination between covalent organic framework（RT-COF-1）with iron ion at 25 ℃.The catalytic conditions of Fe-COF were optimized,and the optimal catalytic activity was determined as follows:the p H of 5.0,the temperature of 35 ℃,the catalyst concentration of 800 g·m L^-1,and the H₂O₂ concentration of 100 m M.The Fe-COF had good p H stability and thermal stability,and it could retain more than 80%activity after being immersed in aqueous solution for 30 days.Under the optimal conditions,the Michaelis constant for hydrogen peroxide was0.196 mmol·L^-1 and for TMB was 0.026 mmol·L^-1.The detection linear range of hydrogen peroxide was 10μM-2000μM,and the minimum detection limit was 5.6μM.The detection system was rapid with high sensitivity in detecting H₂O₂ residue in raw milk,and this catalytic system has high reliability.In addition,the catalytic system was also used to degrade Rh B,and the degradation efficiency reached 88.9%within 30 min.（2）The catalyst CALB@Fe-COF was successfully synthesized by the affinity between metal ions and enzyme molecules using Fe-COF as a carrier.The maximum amount of CALB loading on the Fe-COF was 91.67 mg/g_support,while the specific hydrolytic activity was 53.93U/mg_support.Meanwhile,the CALB@Fe-COF showed better p H stability,thermal stability,organic solvents tolerance and storage stability than that of the free CALB.The conversion rate of the esterification reaction reached 90.7%when the reaction under the optimal conditions（temperature,55°C;molar ratio of substrate,1:1.5;time,6 h）.After recycling 10times,the initial activity of CALB@Fe-COF（55.89%）was higher than that of the N435（29.6%）.（3）The core-shell magnetic covalent organic framework（Fe₃O₄@COF-SA）was successfully prepared with Fe₃O₄ as core,and applied to immobilize the lipase by covalent binding method at 25 ℃.The results indicated that Fe₃O₄@COF-SA@CALB has good magnetic response（34.69 emu/g）.The maximum amount of CALB loading on the Fe₃O₄@COF-SA was 237.1 mg/g_support,while the specific hydrolytic activity was 27.8U/mg_support.Meanwhile,the Fe₃O₄@COF-SA@CALB showed better p H stability,thermal stability,organic solvents tolerance and storage stability than that of the free CALB.The conversion rate of the esterification reaction reached 90.3%when the reaction under the optimal conditions（temperature,50°C;molar ratio of substrate,1:1.5;time,2.5 h）.After recycling 10 times,the initial activity of Fe₃O₄@COF-SA@CALB（78.9%）was higher than that of the N435（29.6%）.